A typical RFID system includes readers and RFID tags. The RFID tags are attached to objects of interest and the readers are used to remotely read the information contained in the tags. Most RFID tags include an antenna connected to a microchip. The antenna is used for communication with the reader and the microchip is used for storing and processing information, modulating and demodulating a radio-frequency signal, and other specialized functions.
RFID systems can be classified based on the frequency used for communication, the power source for the microchip or the method used for conveying information from the RF tag to the reader.
Embedding RFID tags into objects, such as dentures, has several useful applications, such as automated identification, detection, and localization of the objects. For example, detection of dentures can be useful in nursing homes and other long term care facilities for, e.g., the elderly, where frequent loss or misplacement of dentures may be a serious issue. In addition to the cost of replacement, denture loss causes discomfort and deterioration of the health of the denture owners. Not only does a denture owner suffer from poor nutritional intake in the time required to receive a new denture, but he or she may also suffer from the inability to adapt to the new denture.
The problem of denture loss in long term care facilities and hospitals has been analyzed in studies/researches using data gathered from a few such facilities around the world, and these studies/researches suggested techniques, such as visual denture marking and enforcement of staff and resident behavior protocols, in order to combat the problem. Use of RFID for denture identification has also been proposed in several studies. These studies proposed the use of miniature transponders embedded in dentures or tooth implants. Similar studies also suggested the idea of placing the transponders into false teeth (mostly molars). The RFID transponders presented in most of these works are very small and have limited read ranges (e.g., 2-4 inches or shorter) and, therefore, these solutions are more suited to denture identification rather than detection of lost dentures.
U.S. Pat. No. 6,734,795 discusses an RFID system for detection of lost dentures. However, the system uses a combination of a magnetic strip for detection and a close range RFID transponder for identification, wherein a magnetic detector sounds an alarm whenever a magnetic strip embedded in a denture is brought in its vicinity. The range of detection of the system is small (i.e., around 6 to 8 inches), however, and this small range of detection falls short of making a robust and seamless detection system in practical settings. Moreover, because the magnetic strip does not enable identification, the patent also suggests the use of an alternative method, such as visual marking or close range RFID transponders, in combination with a magnetic strip, such that even if a lost denture is detected someone still has to read the visual marking (e.g., name or other markings) or read the information stored in the close range RFID transponder (e.g., using a RFID scanner) to identify the owner of the denture.
A practically viable RFID system for prevention of denture loss requires a much longer range of detection distances. For instance, because lost dentures in many situations may be immersed in or surrounded by high dielectric constant materials, such as water, such RFID system should be able to provide sufficiently long reading range under such varying conditions. Existing RFID tags with long reading range requires relatively bulky antenna or separate power source and thus may not be suitable for being embedded in dentures due to their dimensions, shape and/or substrate. Moreover, these tags are often designed for external attachment to objects and hence their uses are limited for operations in free space. Therefore, even if such tags could be somehow embedded in the dentures, the impedance properties would change due to dielectric effects of the denture material and hence the tag antenna would no longer be tuned to the RFID chip to which the antenna is connected. As a result, the existing commercial off-the-shelf RFID tags may not be suitable for a viable solution to this problem, absent a proper tuning